System of control



Oct. 16 1923.

F. M. PARKS SYSTEM OF CONTROL Filed Dec. 21. 1920 2 Sheets-Sheet 1 Oct. 16, 1923. 1,470,759

F. M. PARKS SYSTEM OF CONTROL Filed Dec 21; 1920 2 Sheets-Sheet 2 dcba dbCz/ WITNESSES: INVENTOR Patented Oct. 16, 1923.

UNITED STATES FRED LE.

PARKS, OF MURRAYSVILLE, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

SYSTEDI OF CONTROL.

Application filed Dcccnibcr 21, 1920. Serial No. 432,332.

To 171/ w/r-mz 1 may (f01lce1'n;

Be it known that I, Fuco M. PARKS, a citmen of the United States, and a resident of Murraysville, in the county of. Westmoreland and State of Pennsylvania, have mvented a new and useful Improvement in Systems of Control, of whichthe following is a specification.

My invention relates to motor'control systems and particularly-to such systerns as'aro employed with cranes, hoists and. similar mechanisms. I The object of :nyinventiomis to'provide means for controlling the speed of an electric motor under all'conditions of load and for accomplishing the desired result smooth ly and without imposing abnormal strains on the motor or other parts of the Systems,

In lowering .a heavy loadon acrane, the operator may suddenly move the handle of the master switch fromrthe full-speed position toward the oti position. Ln t he. 0 8C? ation of the ordinarysystemcfcontro, it is necessary to perform this operation with care and not to effect-dynamic braking. connections until after the motor speedhasbeen considerably reduced. f

According to the present invention, ra.system is provided with a series mobor which is controlled by a masterswitchinsuch manner that, in one direction of rotation,iwhen the load is to be hoisted, the motor-is started in the usual manner with seriesconnectiops, including an acceleratingresiston xThe-speed is readily controlled by shunting. portions of this resistor, the motor-being protected by currenblimit means.

Vhcn it is desired to reverse the motor, as in lowering a load, thearmature connections are reversed and the field-magnet winding is connected in shunt relation to the armature. The accelerating resistor is now connected in series with the field-magnet winding. An auxiliary resistor and the dyna-inic brakting resistor are connected in.the armature circuit in series relation to limit the initial rush of current. The motor starts under the influence of line voltage and also that of the superimposed load to be lowered by the crane. l-Vhen the desired lowering speed is attained. it is thereafter maintained or varicd at the will of the=operator by regulating the strength of the motor, field.

In bringing the load to rest, the operator may, with the present system, return the master switch at once to the olf position and rely on theautomatic .means provided to gradually shunt the resistor from the field circuit to procure graduated regenerative braking prior to disconnecting the motor from the line and prior to establishing the final dynamic brake circuit for stopping and holding the motor. The motor speed is, therefore,.first reduced by increased field excitation before final dynamic braking can be applied My invention will be described in connection .with the accompanying drawings in whichi Fig. 1 is a diagrammatic View of circuits and apparatus embodying my invention;

1 Fig- 2 is a diagrammatic view of the main circuits of thesystem of Fig. 1.

.Fig. 3 is a sequence chart which indicates the order of operation; of the several contactors. a I

The armature- 1, whichflis. connected, through a contactor 2, to a positive'line condoctor 60, has afield-magnet .windingB. A brake-magnetcoil 4 and an accelerating resistor 5 are. connected in series relation and complete the main circuit. through a co tactor 6,-to. a negative line cond uctonfil. Q A dynamicbraking 'resis tor 7 is connected',.in circuitwith the armature and the field-magnet windihg'B :through oontactor 8 and its operating coil 9. Contactors 8 and 6 are so connected mechanicallythat contact 8 opens when contact 6 closes. When the motor is connected for hoisting, namely, with the contactors Zand ti closed the resistor 5 is shunted by contacto'rs'lO, 11. 12 and 13 successively to accelerate the motor. The various speeds in hoisting are selected by a master switch 14.

It maybe assumed that the severiitwntactors are in; their inoperative positions whenpower issupplied from conductors and 61, through the illustrated knife switches, no voltage relay 18- immediately closes, according t a well known practice. To start the hoisting operation, the master switch is operated to its first hoist position a to close contactors'2 and 6 by means of their respective operating coils 15 and 16. The circuit of coil 16 may be traced from the positive line conductor 60, through conductor 17, novoltage relay 18, contact finger19, contact segment 20, coil 16 and conductor 62, to the negative line conductor 61. The circuit of coil 15 extends from no-voltage relay 18,

which is eonneetecl to the positive line co uductor (30, througli-contact fingr 21, cohtzict segment 22 amt coil 15, to conductor (32. The motor circuit extends from line conduc' tor 60, through contactor 2, armature 1, series fielrl-nmg -net. winding 3, brake-magnot. coil 1. resistor relay coil 23 of series relay 24 and rontactor G, to the line conductor 61. I

After the current traversing relay coil 23 drops to a predetermined value, the relay closes, and the accelerating cont actor is closed by its operating coil 25 with the master switch still in the first hoist position. The circuit of coil 25 extends from noveltage relay !8 through contact finger 36.c0n tact segment. 27, relii 24 and coil 25 to conductor 62.

\Vhen the master switch occupies position I, 2'. circuit is established from relay-"18 through cqntqct members 28 and 29, relay 30 mild coil.31 of clont'actor 11 to 'c o iiductor 62. Contector 11 then closes to shu nt a portion of accelerating resistor 5. It'shriuld be th t ea h?wreaths;i e s mechamcally interlocked with econtector, as fire relily S zinc] contaotor 6, so that}. each contactor, in. closing energizes the corresponding relny coil iiritl re'l'ziss' relay from its interlocked posit'io ii; after 'whic elay e 1Pl gente e or he eetiietin' l ef ii ee i sslte s en edd f vh h' r i t e' it i theme n. t it mess g e esy wt-1' were prede mined retire;-

1 si fiij i we aster. w t h. establishes i circuit from the rel; y 1, through m e -swi test i -1 5i? end 3?,

' ey 34 mid. c0 35 qt .s it l twi e e r 2, t er by fiseties he elesi ig 0f contaotor 12 to shunt another portion of resistor 5. y z In position d, the master; sfaiiteh estab{ lishes a circuit through rel qy :18;' master w t vc twts3 an 1 .7, ax, abet-est- .38 n coil 39 h eg i elinst tbereby ef t g t e osi sem ster fliilt i Sh t the rema n g P r ion bi res te fifir I st p ng the ,n t switshli lrsti n to the ofl' position. Thesei ejrzilgonrqctors p n, h reb the mo sirfis fdi enheds e i he. lin .T 't y iiteiebr 'ng ir test w h is inte lid w h the ir tactopfi, is closed, by grzrvityontl held that position by a coil 9.; 1 To reverse the motor to lower the loan}, the

master switch is actusted to the. right, as viewed in Fig. 1, to position q. The contact finger 19 and eontact segment 2t) complete a circuit for the act-tasting coil 16' ofl'contnetor 6, as previouslyjtraced. Contact finger 49 engages contact segment 5!) to complete a circuit-which ex tend s from relay 18 through Contact members 49 1 1rid 50, coils 51 arid 52 of contacts rind 1G, respectivegized by circuits similar to those previously traced, and the contaetors close to shunt the resistor 5 to provide maximum field excitation of the motor. The circuit of the field magnet wir'iding n owextends from conductor 60, through overload relay coil 63, contgictor {10, resistor 41, field-magnet winding 3, brake-magnet coil 4, and contactors 13 and 6, to the negative line, The motor is now connected as 2; shunt motor and operates at; its lowest spee'd under maxiinunrfieid'exci'tetion.

In position b of the master switch, contiictorlii is o ened by the actuation of eont'ec't ,s'e'g len'tfi 3ft 4 out of engagement with eqriract" figer" 36, tireal iin'grtlie circuit of coil 39L o ntiictlor 12 iope rie when its coil 35 3sge-eiirgized'iipofi the separation of eogitects'egihent' 33 frorii contact 32. This ectio? a; section of resistor 5 preiijrous "shu'iiteq bylcoiit aptorsll2 and 13 rind results iifiveakexiih' the' field to iric re'e'se th n l'o' or jp'ee'di A re 51y circuit is e s tigiblished irorfi" reliiy 1s ,"a5;jiewt"5iiger 42 use an t'ajfisziifit; 43,"ii1tefl6pki44 of ooiit'ietor 13 21 11 11,661! toYSopHut The function ofthe 'relj?f"eofiti olI% s51, coil QSQiiiiiiili new closesjts eqntects 7;}? ihd fi flwilljbe ji -t re q r r moto st therftiestef'siyi'teh to position- "'etx e t new e test ei ii ng i e c ireilitofi coi 31 tqppen (io1itect0r l1," lso the separation of 1c: Ii t ti%gipfili 27 firorrr e'oiit'et fifiee e': .ihe-eire mr te w AH iif '1 s is'56'1"5 his 5 h inserted in circuit y'vilih th iiela itifigrietuyvifiqliiig the mptor s eetl furizfieriincreiised; contalctise' iiieiit 54erigages e 'nta t 'fiii 1 ;5 5' t-";';cin t'- it. iir'c'i'iir for erm ne .,i1 9. simtee q ie h i ta te fi sl esteis nft r s s -@411. Iris e um' l ere eef s t i ie s speed th irjt' i mfet reih v'g i-sisto'r 41 from the we we r e a ixee imiirtss s ei 111? ."iqw e er p l in i re or, to stop, the o orator re; turns themgstier s'rr'itcli tower-d1 e ofi. positi 'e- .I e iis e i si k y t e o P tio iihfrdrii fuil l.$pee,"contiictors 10 11, 153 end 1 .1 9 n h rt r 'wm g'radirzill'y strengthe'h the'hqlgl and: diminish the speed 0,f the -rntitorl' cog tactors lt) and 46 115 r'riiiintaiiieci erased duripl'g' the slowdown opratioii. Their ziEtui'x mg coils 51 and 52 are connected across conductors l7 and 62, through relay 18.

Contactor 8 closes only after contactor 13 starts to 'close because it is mechanically interlo xltecl with contact or tithe operating coil of which is maintained energized by the relay 64, and relay 64 does not open until coil 1.5 is de-cnergized upon the'op cning of interlock 44-, and the closure of CQntactor 13. The energization of relay coil 45 is" maintained by a holding circuit through relay 47 and interlock '44. z

W'hcn contactors 10; ll aiid12 hajve'closed. the motor is so r educedfirispe'ed that contactor 8 may be closedftd eii'ect'rlynainic braking. This is accomplished by the closure of contactor 13 to "open the interlock 44, thereby de' energizing rela'yi coil 45, opening comrade-46am de 'eiicrg izing' .coil 16 ofthe dynamic-brakirig'coiitactor 8. The motor is'then bro ught to'rest. f. I

ln a System asds cribedfthe'motor' is controlled "in the hoistinfg dirdctibn in a usual manner; namely.'lacceleration'*Etintjfdlld by current liin'it .de vic esanil deceleration by resistors in tli'e armii fiii circiiitffassisted by the actioii of'hg'ravitfy dr'i the load In the reverse or lowering direct'i'oi'i, thiiihte of deceleration is .no under completecontrol of th'e'op era tor an'd' cans are provided to limit the rate of deceleration, since the action of gravity is adverse.

It will be recognized that a. dynamic-braking resistor of low ohmic value is desirable. inasmuch as braking is usually accomplished from slow speed. However, an operator will frequently attempt to stop a heavy lowering load more quickly than should be attempted, thereby causing the load and the control system to handle excessive currents that produce destructive arcing at the motor commutator and at the control con actors. Undue mechanical strains are also induced. In the present system the equipment is automatically protected. as described, by insuring slow speed of the motor prior to dynamic braking.

I claim as my invention:

1. The combination with an electric motor. and dynamic-braking means for said motor, of means for insuring increased field excitation of said motor prior to dynamic braking, and means for rendering the second means ineffective.

2. The combination with an electric motor and dynamic-braking means for said motor, of means for insuring increased field excitation of said motor prior to dynamic braking. and means comprising a master switch, for rendering the second means ineffective.

3. The combination with an electric motor and dynamic-braking means for said motor, of a relay for insuring increased field excitation of said motor prior to dynamic braking. and a master switch for controlling said motor and for rendering said relay inetlec tive.

4. The combination with an electric motor and .an "accelerating resistor. of dynamic braking means for said motor. means comprising said resistor for controlling the field excitation of said motor prior to drnaznic braking and means comprising a relay and a master switch for controlling dynamhbraking in accordance with the electrical connections or said acceleratinq resistor.

' 5. The combination with an electric motor and an accelerating resistor. of dynamicbralring means comprising a resistor and :r contactor for connecting said resistor in circuit-with said motor. and means comprising: the accelerating resistor for insuring in creased fieldexcitation of said motor prior todynamic braking in accordance with the electrical connections of said accelerating resistorf' i 6. The [combination with an electric motor.

and an accelerating resistor. of a plurality offlcontactors for shuntihg said acceleratingrcsisto'rfa master switch for controlin'g said "contactors, dynamic breaking means comprising a resistor and a contactor "fol-coinnecting'said resistor in circuit with said --motor,'--' means forinsuring increased 'field' excitati'oncf said motor prior to dynamic braking. and means comprising a relay for controlling dynamic braking in response to the closure of said accelerating contactors.

7. The combination with an electric motor and an accelerating resistor. of a plurality of oontactors for shunting said ac elerating resistor a master switch for controlling said contactors, dynamic-hral in means for said motor. means comprising said master switch, said contactors and a rela for the shunting of said accelerating resistor prior to the closing of the dynamic-braking circuit to insure increased field excitation of the motor prior to dynamic braking.

8. The combination with an electric motor and an accelerating resistor, of a plurality of contactors for shunting said accelerating resistor. a master switch for controlling said contactors, means for maintaining the ttIlfiiP ture and field-magnet winding" of said motor in circuit with the source of energy while shuntinp the accelerating resistor for insuring increased field excitation of the motor. dynamic-braking means comprising a resistor and a contactor for connecting said resistor in circuit with the motor and for controlling dynamic braking in response to the operation of one of said accelerating con tactors.

9. The combination with an electric mo or. and an accelerating resist-or. of a plurality of rontactors for shunting said accelerating resistor. means for controlling said contactors, dynamic-braking means comprising a resistor and a contactor for connecting the rcsislor in circuit with said motor, means comprising a plurality of contactors for maintaining the armature and field in circuit with (he source of energy while shuntin; the accelerating resistor, means compris ing said controlling means, said accelerating contactors and a relay XESDODSlYG to the operation of one ofsaid contactors for insuring the shunting of -s aid accelerating resistor prior to the dynamic brakingv of said motor to insure increased field'vexcitation 'prior to dynamic braking.

10. The combination .with an electric motor and an accelerating resistor, of a plurality of contactors for shunting. said ac celerating resistor, means for controlling said contactors, means cqrnprisingutheshunt ing of said accelerating resistor for increasing the field excitation of saidmiotor, means comprising a relay and a plurality of con tactors for maintaining. the motor field and armature circuits priorifodynemie braking and means comprising saidrelay and a master switchv for controlling dynamic braking in response to the operation of said-accelerating contactors. v '11. The combination with an .electric motor and an accelerating resistor, of-ap'lurality of contactors for shunting said accelerating resistor, dynamic-braking means. means for maintaining the motor, a mature and Hold circuits while shunting saiola ccc lerating re sister, to insure increased field excitation of said motor prior to dynamic braking, means sistor, dynamicvbraking means, means for insuring increased field excitation of said motorpripr to dynamic bridging, means for controlling dynarniebralring in response to the operation of the acceleratin .contactors, apd mea i scontrolled by one o the acceleratin contactors fo xdisconnectingthe motor e aad arma u r -ww w e) after a slow speedmf the motorzhasbeen ob tainedfand,substantially simirltaieously with the; application of dynamic braking- In testimony-v whereof, I have hereunto subscribed my name this 9th day of December, 1920. i

FRED M, PARKS. 

